国际前寒武纪地质年代表划分方案研究进展

Study on subdivision scheme of International Precambrian Geological Time Scale

传统的前寒武纪地质年代表划分方案以全球标准地层年龄(GSSA)为基础,不代表任何特殊的岩石实体,仅以推测的绝对测年值为界线进行单元划分,脱离了客观的岩石记录和地球演化系统,不利于对前寒武纪地球系统的研究。2004年—2008年前寒武纪划分参考方案,以反映地球历史阶段特征的"关键事件"为界线,创建前寒武纪地层划分的"金钉子",建立客观的、"自然的"前寒武纪地质年代表,并且通过全球一级事件群把前寒武纪划分为5个宙,即创世宙、冥古宙、太古宙、过渡宙和元古宙。另外,经过综合分析建议将埃迪卡拉纪归到显生宙。因此,对前寒武纪的研究实际上变为对"前埃迪卡拉纪"的研究,使术语"显生宙"在内涵和应用上更加一致。虽然"参考方案"在一定程度上还仅仅是一个理论框架,需要大量的研究去充实和细化,但是对这两种划分方案的系统研究和对比,可以给我国前寒武纪工作者提供重要的研究思路和方向。

Based on Global Standard Stratigraphic Age, the traditional Precambrian Geologic Time Scale was classified by conjectural absolute age values. The unit classified method of boundaries, did not represent any special rock sequence, was incompatible with the objective rock record and earth evolution systera and was unfavorable for the study of Precambrian earth system. The reference scheme of Precambrian Geologic Time Scale for 2004 - 2008 edition, an objective and ＂natural＂ Preeambrian Time Scale, was established by taking ＂key events＂ as boundaries. Also, some Precambrian golden spike profiles were divided by the edition. The Precambrian could be divided into five Evons by the global first-order events that were Genesis Eon, Hadean Eon, Arehean Eon, Transition Eon and Prot- erozoic Eon. Moreover, the Ediacaran period should be classified into Phanerozoic Eon. In fact, the study of Precambrian times should be considered as the study of ＂Preadiacaran＂. Then the connotation and application of term ＂Phanero^oic＂ was more consistent. Although the reference scheme was just a theoretical framework, needing abundance researches to be enriched and refined, the systematically study and contrast of the two Precambrian time scale subdivision schemes could provide important clues for the Chinese geologists for Precambrian research.